If the season length isn't set as default, there is a high possibility of another deerclops spawn at the start of the next season of winter.
Here are a few combinations that I found to spawn the second deerclops.
Long/very long non-winter season + very short to very long winter + any length of the left 2 seasons
I don't know the detail of giants spawning mechanism, but I prefer a more reasonable one, lol.
1. Set the autumn season length of a world as very long. 2. Jump to the first winter, wait for the first deerclops spawn and kill him. 3. Jump to the first day of spring, skip one day to see another deerclops spawn.